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Russian Peasant algorithm go
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package main | |
import ( | |
"fmt" | |
"time" | |
) | |
func main() { | |
num1 := 2000000000 | |
num2 := 2000000000 | |
start := time.Now() | |
a := naive(num1, num2) | |
elapsed := time.Since(start) | |
fmt.Printf("Product: %d, Elapsed Time: %d \n", a, elapsed) | |
start = time.Now() | |
a = russian(num1, num2) | |
elapsed = time.Since(start) | |
fmt.Printf("Product: %d, Elapsed Time: %d \n", a, elapsed) | |
start = time.Now() | |
a = recRussian(num1, num2) | |
elapsed = time.Since(start) | |
fmt.Printf("Product: %d, Elapsed Time: %d \n", a, elapsed) | |
} | |
func naive(a, b int) int { | |
x := a | |
y := b | |
z := 0 | |
for x > 0 { | |
x = x - 1 | |
z = z + y | |
} | |
return z | |
} | |
func russian(a, b int) int { | |
x := a | |
y := b | |
z := 0 | |
for x > 0 { | |
if x%2 == 1 { | |
z = z + y | |
x = (x - 1) / 2 | |
} else { | |
x = x / 2 | |
} | |
y = y * 2 | |
} | |
return z | |
} | |
func recRussian(a, b int) int { | |
if a == 0 { | |
return 0 | |
} | |
if a%2 == 0 { | |
return 2 * recRussian(a/2, b) | |
} else { | |
return b + 2*recRussian((a-1)/2, b) | |
} | |
} |
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